Habitat use and foraging behavior of male Black-and-white Warblers (Mniotilta varia) in forest fragments and in a contiguous boreal forest

Abstract

We examined habitat use and foraging behavior of male Black-and-white Warblers (Mniotilta varia) in fragments (2-140 ha) of mature forest dominated by trembling aspen (Populus tremuloides) and a similar contiguous forest (Ͼ1000 ha) in central Alberta, Canada. Vegetation structure and composition differed significantly between occupied and unoccupied fragments, and between plots within and outside territories in occupied fragments. Territories in fragments were characterized by a high abundance of willow (Salix spp.), which was the primary foraging site for males in this habitat. Territories in contiguous forest differed significantly in vegetation structure from territories in fragments, and were characterized by a high abundance of trembling aspen trees, which served as the primary forest foraging site. The use of foraging substrates and foraging methods did not differ between individuals in fragments versus contiguous forest. In the boreal mixedwood ecoregion, the Black-andwhite Warbler appears flexible in its habitat use.